Ligation of an archwire to an orthodontic bracket is one of the most time consuming and frequently repeated procedures that is practiced during orthodontic treatment. Ligation typically has been performed using elastic "O" rings or soft stainless steel ligature ties. The placing and removing of "O" rings and ligature ties are time-consuming and tedious tasks which increase patient chair side time and expense. In general in these procedures the archwire is first inserted into the archwire slots of the brackets, which are already fixed to the teeth. The archwire is then locked into the slots by placing the ligation member over the archwire and engaging one or more tie wings to thereby securely hold the archwire in place. The ligature is intended to continuously force the archwire to the bottom of the slot.
In various types of brackets it is the bottom of the slot which is configured to align the teeth in their correct position along the continuous length of the archwire. Hence, if the ligature does not continuously force the archwire to the bottom of the slot, the alignment of the teeth may be compromised. One drawback of elastic "O" rings is that they tend to lose their elasticity in a very short period of time, so that the force needed to secure the archwire in the bottom of the slot is no longer present. Thus, the archwire is able to rotate, resulting in an undesirable alignment. To avoid this result, elastic "O" ring ligatures must be replaced quite frequently. Similarly, soft stainless steel ligature ties tend to rapidly lose their retentive forces on the archwire and also must be replaced frequently.
Alternatively, there are various bracket designs that have attempted to eliminate the need for a ligature altogether. For example, "Activa" produced by A Company, "Speed" and "Edgelock" produced by Ormco Corporation, and others are typical examples of ligature-less brackets that are commercially available. All of the above examples, although facilitating orthodontic procedures, have compromised certain design features of the bracket. For example, slot cavities have been designed to have a certain fixed size that is necessarily greater than the largest possible orthodontic wire commercially available; self ligation features add to the overall height of the bracket, making it more uncomfortable for the patients; and the locking mechanisms in the self ligation systems significantly limit the possibility of providing other desirable features, such as hooks, on the bracket.
Therefore, what is needed is a self-ligating bracket which overcomes the various drawbacks mentioned above and provides sustained archwire-retaining forces during the course of orthodontic treatment.